A semiconductor device may include an n-channel metal oxide semiconductor (NMOS) transistor having an extended drain. There are several possible configurations for the NMOS transistor. The NMOS transistor may be used to modulate current through a load in a high-side configuration, with the NMOS transistor being connected between the load and a positive power supply node. In this configuration, the NMOS transistor may be isolated from the substrate, with the source of the NMOS transistor connected to the load, so the potential of the source varies with respect to a ground reference. Alternatively, the NMOS transistor may be used to modulate current through a load in a low-side configuration, with the NMOS transistor being connected between the load and a ground node. In this configuration, it may be desirable to modulate the potential of the body of the NMOS transistor to reduce on-state resistance and increase off-state resistance. The semiconductor device may also include logic circuits operating at 5 volts or less, while the positive power supply node connected to the NMOS transistor may have a potential significantly higher than the logic circuits, for example, 20 volts to 40 volts, or more. Integrating such an NMOS transistor with the logic circuits while keeping fabrication cost and complexity under control has become more problematic as the dimensions and operating voltages of the logic circuits have become smaller with each new logic technology node.